endocrinology of pregnancy

Question 1

tubular fluid reabsorption in rete testis and epididymis is under what control?

Answer 1

oestrogen

Question 2

nutrient and glycoprotein secretion into the epididymal fluid is under what control?

Answer 2

androgen

Question 3

what are the functions of these secretions?

Answer 3

• provide energy for jounrey

- coat surface of spermatozoa (protection)

Question 4

where is semen ejaculated to? how much spermatozoa enter cervix?

Answer 4

• ejaculated into vagina or cervical canal

- 1%

Question 5

what does sperm consist of?

Answer 5

• spermatozoa
• seminal fluid
• leucocytes (so potentially viruses, e.g. Hep B, HIV)

Question 6

where is seminal fluid produced?

Answer 6

• epididymis/testes (small contribution)

- accessory sex glands (major contribution)

Question 7

what are these accessory sex glands?

Answer 7

• seminal vesicles (produce fructose and fibrinogen)
• prostrate (produce citric acid)
• ampulla
• bulbourethral

Question 8

what is capacitation of sperm?

Answer 8

• in seminiferous tubule, spermatozoa are incapable of fertilizing an ovum
• in vas deferens, they are capable of movement but have little capability of fertilisation
• full activity, spermatozoa must undergo capacitation in oviduct

Question 9

what is the order of capacitation?

Answer 9

• loss of glycoprotein coat
• change in surface membrane characteristics
• whiplash movements

Question 10

what is needed for capacitation?

Answer 10

• oestrogen dependant

- requires Ca2+ for all activities

Question 11

what does fertilisation occur in?

Answer 11

fallopian tubes

Question 12

what does fertilisation result in?

Answer 12

• expulsion of second polar body (of ovum)
• leads to immediate zona reaction (degradation of ZP3 coat)
• this prevents further binding (Ca dependent)

Question 13

What is the Ca influx into the sperm stimulated by?

Answer 13

• progesterone

- and as a result of G-protein mediated action following the binding of sperm to ZP3

Question 14

what is the cortical reaction?

Answer 14

breakdown of zona pellucida by granules containing digestive enzymes to break down coat

Question 15

when does the zygote start dividing?

Answer 15

once diploidy is established

Question 16

what is the Ca-dependent acrosome reaction?

Answer 16

• enables capacitated spermatozoa to bind to and pennetrate the zona pellucida by releasing haluronidase

Question 17

what is the conceptus?

Answer 17

fertilised ovum

Question 18

what then happens to the conceptus?

Answer 18

• continues to divide as it travels down the oviduct (3-4 days)
• receieve nutrients from uterine secretions
• conceptus first compacts to an 8-16 cell morula
• then it becomes a blastocyst
• then transferred to uterus at this stage facilitated by inc. progesterone: oestrogen ratio

Question 19

describe a blastocyst

Answer 19

2 separate cell populations

• inner mass (becomes embryo)
• outer trophoblast (becomes chorion)

Question 20

what does implantation involve?

Answer 20

• attachment phase: outer trophoblast cells contact uterine epithelium
• decidualisation: of underlying stromal tissue

Question 21

what does implantation require?

Answer 21

progesterone domination in presence of oestrogen

Question 22

what does leukaemia inhibitory factor from endometrium stimulate?

Answer 22

adhesion of blastocyst to endometrium

IL-11 also involved

Question 23

what is decidalisation?

Answer 23

invasion of underlying uterine stromal tissue by outer trophectoderm cells of blastocyst

Question 24

what happens in decidualisation within hours?

Answer 24

• inc. vascular permeability in invasion region (oedema)
• localised changes in intracellular composition (glycogen accumulation in cytoplasm)
• progessive sprouting and growth of capillaries (decidulaisation reaction)

Question 25

what are the factors invovled in decidualisation?

Answer 25

• IL-11
• histamine
• prostaglandins
• TGF-beta (angiogenesis)

Question 26

what happens in the first 5-6 weeks of pregnancy?

Answer 26

• maternal ovaries release gonadal steroids
• circulating progesterone and oestradiol conc are high and rising
• this inhibits release of materal LH and FSH

Question 27

as LH and FSH are inhibited, what is the stimulatory role on corpus luteum taken over by?

Answer 27

hCG produced by developing blastocyst

Question 28

what happens from day 40 of pregnancy?

Answer 28

• ovariectomy has no effect on pregnancy

- role of corpus luteum taken over by foetalplacental unit

Question 29

what maternal hormones increase in pregnancy?

Answer 29

• ACTH (pregnany activated stress axis)
• prolactin (suppresses GnRH)
• iodothyronines (pregnancy inc. metabolic rate, driven by hCG not TSH, so TSH falls)
• adrenal steroids (more ACTH so more cortisol)
• PTHrp (parathormone related peptide, more Ca required for lactation)

Question 30

what maternal hormones decrease in pregnancy?

Answer 30

• gonadotrophins
• TSH (falls as hCG stimulates high T4)
• hCG (placental variant inc)

Question 31

generally, what happens in parturition?

Answer 31

oxytocin –> raised intracellular calcium –> contraction

Question 32

what does contraction occur by?

Answer 32

• by calcmodulin activating calmodulin-myosin kinase which cintracts actin-myosin

Question 33

what does oestrogen stimulate that leads to raised intracellular Ca?

Answer 33

• oestrogen stimulates phospholipase A2
• stimuates arachidonic acid to PGF2a production
• raises intracellular Ca from microsomes
• Ca can also enter from outside

Question 34

what hormones are involved in lactation?

Answer 34

• oxytocin stimulates milk ejection

- prolactin stimulates milk synthesus